On the heels of the Feb. 4, 2023, shooting down of a Chinese balloon suspected of spying on the U.S., American fighter jets have shot down three additional objects in or near U.S. airspace.

When the media asked Glen VanHerck, the Air Force general responsible for overseeing North American airspace, about these events, he refused to rule out extraterrestrial forces at play. Other military officialslater clarified that otherworldly origins aren't a serious consideration, but the comment highlighted the U.S. government's lack of knowledge about these objects.

As a space policy expert, I'm often confronted with questions about UFOs and little green people. However, as these recent episodes have shown, a UFO is far more likely to be human-made, rather than originating from some faraway place in the universe.

Novel propulsion ideas for moving around space seem like they're a dime a dozen recently. Besides the typical argument between solar sails and chemical propulsion lies a potential third way—a nuclear rocket engine. While we've discussed them here at UT before, NASA's Institute of Advanced Concepts has provided a grant to a company called Positron Dynamics for the development of a novel type of nuclear fission fragment rocket engine (FFRE). It could strike the balance between the horsepower of chemical engines and the longevity of solar sails.